This invention generally pertains to disk brakes and more particularly to a unique configuration for a torque tube, drive key, and backplate assembly which may be applied to various type disk brake applications. More specifically, the invention provides a torque tube having separable and replaceable keys and a separable and replaceable backplate. While the invention will be described herein with regard to aircraft wheel and brake configurations, it may as well be applied to other type vehicle disk brake configurations and various industrial brake applications. The invention therefore, is not considered limited in scope by the specific application illustrated in the drawings.
By way of example, FIG. 1 of the drawings is illustrative of a conventional prior art aircraft wheel and brake assembly generally indicated by reference numeral 10. Portions which are pertinent to the invention are indicated in solid lines while less pertinent portions are indicated via ghost lines for the purpose of illustrating the environment thereof. Very generally, a wheel and brake assembly 10 may include a two-part wheel 12 comprised of an inboard wheel half 12a and an outboard wheel half 12b which are fastened together by a plurality of wheel bolts 12c and mounted for rotation about an axle 14 via a plurality of wheel bearings diagramatically indicated at 16. A multi-disk brake assembly generally indicated by reference numeral 20 may be mounted at the inboard side of the wheel 12 within the wheel cavity formed by the inboard wheel half 12a. The brake assembly 20 includes a torque tube 30 mounted via a plurality of bolts 32 to a brake housing 34 having brake actuating means 36 for applying a braking pressure to a pressure plate 38. The pressure plate 38 transmits the braking pressure to a brake stack generally indicated by reference numeral 40 to effect braking of the wheel 12. Wheel braking action is accomplished by the brake stack 40 comprised of alternating brake disks 42 and friction disks 44 either one of which may be keyed for rotation with the wheel 12 or alternatively keyed to be relatively stationary with the torque tube 30. As illustrated in the drawing, the outer periphery of the rotating members of the brake stack 40 are keyed to the inner periphery of the inboard wheel half 12a while the inner periphery of the stationary members of the stack 40 are keyed to the outer periphery of the torque tube 30. Thus, the torque tube 30 plays a primary role in the braking action and the design and construction of it is critical to the effectiveness of the brake system.
Conventionally, torque tubes of the prior art as illustrated in FIG. 1 may comprise a one-piece forged or cast metal member 30 that is machined to close tolerances to provide the keyed interconnections for the stationary members of the brake stack 40. Conventional torque tubes 30 of the prior art may also be characterized by an integral backplate 30b that extends radially at an approximate angle of 90 degrees with respect to the cylindrical portion 30a of the tube and which operates to engage the brake stack 40 when a braking pressure is applied at the opposite end by the actuating means 36 through the pressure plate 38. The prior art torque tube may further be characterized by a tubular portion 30a that carries the keying elements 30c for engagement with the stationary members of the brake stack 40 and these keying elements are conventionally machined into the outer peripheral surface of the torque tube.
Problems associated with conventionally forged or cast and machined torque tubes 30 involve the backplate 30b and the drive key elements 30c. The backplate 30b may develop fractures due to the axial force exerted on it and heat buildup during braking while the keys 30c suffer wear associated with braking action. In this circumstance, and because the backplate and keys are made as an integral part of the torque tube, the total torque tube must be replaced to put the brake assembly back into a safe and reliable operating condition. In this respect, the torque tube 30 is usually the single most expensive element of a typical brake assembly and therefore replacement of it is a major maintenance operation and an expensive proposition.
In view of the above mentioned disadvantages of the presently used torque tube, it is in one aspect of the present invention an object to provide a torque tube assembly that eliminates replacement of the total torque tube when failure occurs to the backplate and/or drive key portions of the assembly.
In another aspect of the invention it is an object to provide a torque tube that is more economical to manufacture and which does not require extensive machining operations and elaborate inspection techniques to meet rigid aircraft and/or industrial specifications.
In another aspect of the invention it is an object to provide a torque tube assembly that has separable drive keys which may be individually replaced when worn or defective keys are detected.
In still another aspect of the invention it is an object to provide a torque tube assembly having a separable backplate that may be easily replaced when such backplate suffers fatigue failure and/or other defects.
In another aspect of the invention it is an object to provide a torque tube that exhibits a longer service life than experienced with presently used one-piece torque tubes and wherein the operational integrity may be more easily tested, and which may be applied to brake assemblies having different diameters and numbers of drive keys.